The long-term objective of this proposal is to elucidate the cellular machinery critical for the processing of toxic protein aggregates and its role in the pathogenesis of neurodegenerative disease. The cocentration of protein aggregates to a specialized inclusion body, the aggresome, has emerged as a critical cellular response to the pathological accumulation of misfolded proteins. The clinical relevance of aggresomes is implicated by its striking similarity to Lewy bodies, the pathohistological hallmark of Parkinson's and other neurodegenerative diseases. We have discoverd that the microtubule-associated deacetylase HDAC6 is a componet of Lewy bodies and plays a critical role in aggresome formation. Loss of HDAC6 results in a failure in aggresome formation and pronounced cell death in response to misfolded protein accumulation. We hypothesize that HDAC6 protects neurons by recognizing and facilitating the transport of ubiquitinated protein aggregates to aggresomes/Lewy bodies, thereby preventing neurodegeneration caused by toxic protein aggregates. We propose: Aim 1. To delineate the function of the HDAC6 complex in ubiquitin-dependent misfolded protein processing. We will charaterize the ubiquitin-binding activity of HDAC6 complex and determine the nature and functions of poly-ubiquitin modification in misfolded protein processing and aggresome formation . Aim 2. To characterize the role of HDAC6-mediated deacetylation in misfolded protein processing and aggresome formation. We will determine how protein acetylation regulates the function of the misfolded- protein ubiquitin ligase CHIP and the transport of misfolded proteins by the microtubule network. Aim 3. To characterize the role of HDAC6 in the pathogenesis of Parkinson's disease. We will determinie whether HDAC6 knockout mice are defective in forming Lewy bodies and more susceptible to neurodegeneration in response to Parkinsonism-inducing mutant a-synuclein expression. The accumulation of toxic protein aggregates has emerged as a common cause of neurodegenerative diseases. By characterizing the mechanism and protein machinery that eliminate toxic protein aggregates, we hope to identify new avenues for developing novel therapeutic approaches for treating neurodegenerative disease.